After an initial phase in which virtually pure crude oil is recovered, the major part of the crude oil produced is obtained as a water-in-oil emulsion.
Before transportation, the water must be separated off or reduced to an acceptable concentration. This is generally done by adding oil demulsifiers, separation being facilitated and accelerated by heating the crude oil. The compositions of the crude oil emulsions vary greatly depending on the source; hence, a large number of different oil demulsifiers are used worldwide in order to achieve optimum demulsification results. However, there is great interest in improved demulsifiers to provide more rapid separation into oil and water and give good residual amounts of water and salt when used with a very wide variety of crude oil emulsions.
The most frequently used demulsifiers are ethylene oxide/propylene oxide block polymers, oxyalkylated alkylphenol/formaldehyde resins, oxyalkylated polyamines and in particular crosslinked products of the above basic classes with multifunctional reagents, eg. diisocyanates, dicarboxylic acids, bisglycidyl ethers and di- and tri- methylolphenol.
Polymeric oil demulsifiers have also been disclosed (Canadian Patent 1,010,740 and De-C1 33 38 923).
According to this Canadian patent, oxyalkylated alcohols and oxyalkylated alkylphenol/formaldehyde resins are etherified with unsaturated glycidyl compounds (eg. glycidyl acrylate), esterified with maleic anhydride or fumaric acid or transesterified with acrylates or methacrylates in order to introduce unsaturated functions which can be subjected to free radical polymerization and are polymerized in a subsequent reaction with other monomers in solution. DE-C1 33 38 923 describes products which are obtained by copolymerizing polyoxyalkylene ethers of allyl or methallyl alcohol with vinyl esters or acrylates or methacrylates.
All these products have weaknesses with regard to their activity or arising from the preparation process. For example, the use of glycidyl compounds for introducing the unsaturated function during the polymerization frequently results in the formation of gels and inhomogeneities, derivatives of allyl alcohol, methallyl alcohol and maleic acid give rise to poor copolymerization conditions, and difficulties are encountered in the transesterification with acrylates or methacrylates with regard to complete, selective esterification of the oxyalkylated starting alcohols, some of which are multifunctional.
Furthermore, the copolymers frequently undergo reactions leading to gelling and solidification, particularly where multifunctional starting alcohols are used in the oxyalkylation. However, products having high potential activity and a broad spectrum of uses are obtainable precisely through the use of oxyalkylated multifunctional alcohols.
We have found, surprisingly, that copolymers which are suitable as oil demulsifiers and are obtained from hydrophobic acrylates or methacrylates, whose alcohol component is derived from a mixture of polyglycols and polyglycol ethers, with hydrophilic ethylenically unsaturated comonomers have a long shelf life and high efficiency if, in this copolymer (i) all or virtually all of the free OH groups are etherified, esterified or converted to urethane groups and/or (ii) the acid used as a catalyst during the esterification is neutralized by adding an amine.
The mixture of polyglycols and glycol ethers used for the esterification consists as a rule of oxyalkylates of the formula EQU R.sup.1 --O--[AO].sub.x --H
where R.sub.1 is a radical of a monohydric or polyhydric alcohol or alkylphenol or a radical of an alkylphenol/formaldehyde or alkylphenol/acetaldehyde condensate, AO is an ethylene oxide, propylene oxide or 1,2-butylene oxide radical, a mixture of these radicals or blocks of these radicals, and X is from 5 to 120.
The present invention relates in particular to copolymers in which
A) acrylates or methacrylates of oxyalkylates of the formula EQU R.sup.1 --O--[AO].sub.x --H PA1 where R.sup.1, AO and x have the above meanings are copolymerized with PA1 B) hydrophilic comonomers of the formula ##STR1## where R.sup.2 is hydrogen, ##STR2## PA1 C) the free OH groups are converted to an unreactive form by etherification, esterification or urethane formation, and/or the acid used as a catalyst in the preparation of the ester in A) and/or in the esterification in C) is neutralized with a tertiary amine. PA1 1) Mixing with an oxyalkylated alcohol or a mixture of several oxyalkylated alcohols, such as those obtained as described under a), or with other copolymers from B) and C) in a ratio of from 10:90 to 90:10, preferably from 50:50 to 80:20. Better efficiencies can also be obtained by adding cosurfactants to the copolymers in amounts of from 5 to 30% by weight. Examples of such cosurfactants are dodecyl bisulfate, alkylbenzenesulfonates and alkylnaphthalenesulfonates. PA1 2) The molecular weight can be increased by subsequent crosslinking with multifunctional crosslinking reagents which react with reactive groups of the copolymer. The crosslinking reactions are carried out (depending on the type of crosslinking agent) using from 0.1 to 10, preferably from 1 to 4%, by weight of multifunctional components at from 80.degree. to 140.degree. C. For example, the following multifunctional crosslinking agents are used, depending on the comonomers employed: bisglycidyl ethers (preferably bisglycidyl ethers of bisphenol A), multifunctional alcohols (eg. sorbitol or ethylene glycol), diisocyanate (eg. toluene diisocyanate) and similar compounds which react with reactive centers on the copolymer. PA1 3) Subsequent oxyalkylation with an alkoxide, a mixture of several alkoxides or blocks containing different alkoxides. The copolymers from B) and C) are reacted with the alkoxide(s) using basic catalysts (preferably sodium hydroxide or potassium hydroxide) in amounts of from 0.5 to 5% by weight and at from 100.degree. to 150.degree. C. Preferred alkoxides are ethylene oxide, propylene oxide and 1,2-butylene oxide, the ratio of copolymer to alkoxide varying from 5:95 to 95:5. PA1 4) Quaternization of N-containing copolymers with known quaternizing agents, such as dimethyl sulfate or methyl iodide, at from 50.degree. to 120.degree. C. The amine functions present can be completely or only partially quaternized.
R.sup.3 is hydrogen or --COOH and R.sup.4 is hydrogen or --CH.sub.3, with the proviso that one or more of the groups R.sup.2 and R.sup.3 is a hydrophilic group, the weight ratio of A) to B) being from 300:1 to 1:50, and
The conversion of the free OH groups can also be carried out before the polymerization, and some of them may even be converted before the preparation of the ester comonomer.
The copolymers are prepared in a conventional manner, for example by free radical copolymerization in solution, emulsion or suspension.
The esterification of the acrylic acid or methacrylic acid is preferably effected in the presence of an acidic esterification catalyst and using an entraining agent.
Suitable esterification catalysts are conventional inorganic or organic catalysts, such as sulfuric acid, p-toluenesulfonic acid, dodecylbenzgnesulfonic acid, hydrochloric acid or acidic ion exchangers.
Examples of entraining agents are conventional organic solvents which form an azeotrope with water, in particular xylene or toluene.
Examples of suitable agents for the etherification of the free OH groups are methyl iodide, dimethyl sulfate and benzyl chloride.
Carboxylic anhydrides, such as acetic anhydride, maleic anhydride, phthalic anhydride or succinic anhydride, are preferably used for esterifying the free OH groups.
The conversion of the free OH groups to urethane groups, ie. the preferred reaction of the copolymerization, is advantageously carried out in a conventional manner by the action of isocyanates, for example using phenyl isocyanate or stearyl isocyanate.
To neutralize the acids used as an esterification catalyst, amines, preferably tertiary amines, are added. Specific examples of suitable amines are triethylamine, tributylamine, dimethyl-Cy-amines (where y is C.sub.8 -C.sub.18) and triethanolamine.
Specifically, the following procedure is adopted, for example, in the preparation of the novel polymers. Preparation of the oxyalkylates of the formula R.sup.1 --O--[AO]--H a) Preparation of the oxyalkylated alcohols
The oxyalkylated alcohols are prepared in a conventional manner by reacting the monofunctional or multifunctional alcohol with an alkoxyide or a mixture of several alkoxides or blocks of several alkoxides, using a basic catalyst at from 80.degree. to 160.degree. C. Examples of suitable alcohols are ethanol, butanol, isopropanol, tallow fatty alcohol, stearyl alcohol, alkylphenols of the general formula ##STR3## where R is, for example, C.sub.9 H.sub.19, CH.sub.3, CH(CH.sub.3).sub.2, C(CH.sub.3).sub.3 or C.sub.8 H.sub.17, ethylene glycol, propylene glycol, bisphenol A, glycerol, trimethylolpropane, pentaerythritol, sorbitol, polyglycerol or the alkylphenol/formaldehyde or acetaldehyde condensates described below.
Preferred alkoxides are ethylene oxide, propylene oxide and 1,2-butylene oxide or mixtures of these.
The reaction conditions vary depending on the type and amount of the alkoxides used. In general, the reaction temperature is from 80.degree. to 160.degree. C., and the amount of basic catalysts varies from 0.25 to 5%, potassium hydroxide and sodium hydroxide being preferred. Depending on the consistency of the starting alcohol and end product, an inert solvent which does not influence the reaction may be added to effect dilution. Xylene is preferred.
The ratio of alcohol to alkoxide(s) can vary greatly but is advantageously from 1:120 to 1:5.
b) Oxyalkylated alkylphenol.formaldehyde or acetaldehyde condensates
The alkylphenol/formaldehyde or acetaldehyde resins used as alcohols for the oxyalkylation are prepared in a conventional manner by reacting the aldehyde with the alkylphenol in a ratio of from 2:1 to 1:2, preferably 1:1.05, by a base-catalyzed or acid-catalyzed reaction, preferably the latter, at from 80.degree. to 250.degree. C., using a high boiling solvent for completely removing the resulting water of reaction in the form of an azeotrope. The alkylphenol used is, for example, nonylphenol, tert-butylphenol or octylphenol, and preferably used aldehydes are formaldehyde and acetaldehyde. In general, an alkylsulfonic acid or alkylbenzenesulfonic acid, eg. dodecylbenzenesulfonic acid is preferably used as the catalyst, in an amount of from 0.2 to 2%, preferably from 0.2 to 0.5%.
At the beginning of the reaction, the temperature is kept at 90.degree.-120.degree. until the major part of the water of reaction has distilled off. Thereafter, the mixture is heated to the boiling point of the solvent in order to complete the reaction, and the residual amount of water is removed as an azeotrope. The molecules contain on average from 4 to 12, preferably from 5 to 9, aromatic nuclei.
The condensates thus obtained are oxyalkylated as stated under a).
c) Conversion of some of the free OH groups of the alkoxides from a) and b)
When the oxyalkylation is complete, the alkoxides from step a) or b) can be reacted in order to block some of their terminal groups, blocking of from 20 to 90% of the terminal OH groups being preferred. This step can be carried out by acid-catalyzed esterification with a carboxylic anhydride, preferably acetic anhydride, phthalic anhydride, succinic anhydride or maleic anhydride, at from 50.degree. to 130.degree. C., or by reacting the alcoholates with dimethyl sulfate, benzyl chloride or methyl iodide, the alkylating agent being added to the sodium or potassium alcoholates at from 40.degree. to 80.degree. C., and by reaction with isocyanates.
A) Conversion of the oxyalkylates to monomers
Since the demulsifiers for crude oil emulsions must be surfactants, the extent of their hydrophilic or hydrophobic nature is adjusted via the ratio of the polyethylene oxide block (hydrophilic) to the polypropylene oxide block (hydrophobic) to the hydrophilic comonomers (eg. acrylic acid). Since, in order to achieve maximum efficiency, these products must be soluble in crude oil, it is important that hydrophilic polyacrylic acid moiety in the copolymer is kept in solution in an aromatic solvent (eg. toluene, xylene or a mixture of aromatics) by a large hydrophobic radical. This is achieved only by complete, selective introduction of a functional group which can be subjected to free radical polymerization into the hydrophobic oxyalkylated alcohol, some of whose terminal groups may be blocked, and the use of the said alcohol in the subsequent free radical copolymerization with hydrophilic comonomers.
To introduce the unsaturated functional groups into the said alcohols, the latter are esterified with acrylic acid or methacrylic acid in the presence of an acidic catalyst (eg. p-toluenesulfonic acid, sulfuric acid or dodecylbenzenesulfonic acid) at from 80.degree. to 150.degree. C., the necessary complete removal of the water of reaction being effected by means of an azeotropic entraining agent, preferably toluene or xylene.
In order to prevent polymerization during the esterification, it is advisable to use stabilizers which are known per se (preferably hydroquinone monomethyl ether). The ratio of the oxyalkylated alcohol to acrylic acid or methacrylic acid may be varied from 1:1 to 1:n, where n is the functionality (ie. the number of hydroxyl groups) of the starting alcohol. A ratio of 1:1 is preferred, since otherwise gelling may be observed during the subsequent polymerization. Complete esterification of the acrylic acid or methacrylic acid is advantageously monitored by analytical methods (eg. the acid number). The amount of stabilizer varies from 0.3 to 2% by weight and is preferably 1% by weight, the percentages being based on the amount of acrylic acid or methacrylic acid. The acid catalyst is added in an amount from 0.5 to 5, preferably from 2 to 3%, by weight. Equally good esterification results are obtained by using acrylic anhydride or methacrylic anhydride and acryloyl chloride or methacryloyl chloride. In this procedure, removal of the water by azeotropic distillation is dispensed with.
The weight ratio of the solvent to the total amount of oxyalkylated alcohol and unsaturated carboxylic acid can vary from 30:70 to 70:30, a ratio of from 50:50 to 30:70 being preferred.
After esterification with acrylic acid or methacylic acid, any hydroxyl functions still present can be blocked using carboxylic anhydrides and isocyanates. Phthalic anhydride, acetic anhydride and maleic anhydride are preferred. All of the hydroxyl groups can be blocked by using equimolar amounts of anhydrides, alkylating agents or isocyanates, or at least some of the hydroxyl groups can be blocked. Preferably, from 70 to 100% of the terminal hydroxyl groups still present are converted. The anhydride or isocyanate is added to the solution of the acrylate or methacrylate, in the presence or absence of a catalyst, and, depending on the reactivity, the reaction is complete in the course of from 0.5 to 5 hours and from 70.degree. to 120.degree. C.
When the esterification is complete, the added catalytic amounts of acid can be neutralized by adding equimolar amounts of amines, eg. triethanolamine, triethylamine or tributylamine. However, the acids are preferably neutralized after polymerization and any condensation have been carried out.
B) Copolymerization of the oxyalkylate monomers from A) with hydrophilic comonomers
The copolymers can be prepared by solution, emulsion or precipitation polymerization, solution polymerization in a nonpolar solvent (such as toluene or xylene), being preferred. The comonomer or a mixture of several comonomers is added to, or introduced dropwise to a solution of the esterified, oxyalkylated alcohol in which the terminal groups may have been blocked, or a mixture of several different esterified oxyalkylated alcohols from A) in which the terminal groups may have been blocked, and the reaction is carried out with the aid of known free radical initiators at from 60.degree. to 140.degree. C. Typical comonomers are acrylic acid, methacrylic acid, maleic anhydride, hydroxyethyl acrylate, N,N-diethylaminoethyl acrylate, acrylamide, acrylonitrile, vinyl acetate, allyl alcohol, vinylformamide, vinylimidazole, vinylpyrrolidone, fumaric acid, maleic acid, N,N-dimethylacrylamide and vinyl methyl ether, acrylic acid, possibly as a mixture with other comonomers in a ratio of from 10:1 to 1:1, being preferred.
Suitable free radical initiators are, as a rule, 2,2'-azobisisobutyronitrile (AIBN), dibenzoyl peroxide, tert-butyl peracetate and 2,2-azobis-2,4-dimethylvaleronitrile, AIBN and dibenzoyl peroxide being preferred. The amount of free radical initiators used is, as a rule, from 0.1 to 2% by weight, based on the total monomer content. In order to achieve a very low concentration of residual monomers, a reaction time corresponding to five times the half life of the initiator at the chosen reaction temperature is preferable. The exothermic copolymerization can be optimized in respect of the heat of reaction, molecular weight distribution and residual monomer content by the dropwise addition of the free radical initiator, in the presence or absence of known molecular weight regulators, such as mercaptans or aldehydes, and with or without the simultaneous addition of (one part) of the comonomer. A single initial addition of from 0.1 to 0.8% by weight of AIBN to the solution of the ester and of the comonomer and polymerization at from 60.degree. to 90.degree. C. in the course of from 2 to 5 hours, as well as a continuous metering of AIBN to the solution of the ester and comonomer (with or without initial addition of AIBN to the solution) in the course from 0.5 to 3 hours at from 60.degree. to 90.degree. C., in the presence or absence of molecular weight regulators, such as mercaptans or aldehydes, in amounts of from 0.05 to 1% by weight, based on the comonomer, are preferred. The simultaneous use of several esterified oxyalkylated alcohols in which the terminal groups may be blocked, and the addition or metering of several comonomers, are also possible but do not constitute a preferred procedure. The polymerization concentrations are from 20 to 70, preferably from 40 to 60%, by weight. To obtain efficient products, it is sometimes advisable to carry out a preliminary polymerization of the hydrophobic ester of the oxyalkylated alcohol and acrylic acid or methacrylic acid, in which the terminal groups may be blocked, in the course of from 1 to 2 hours using the above free radical initiators, and then to add or continuously meter in the comonomer over from 1/3 to 2/3 of the reaction time, possibly with additional radical initiator.
The K values of the resulting polymers are in general from 15 to 60 (measured in 1% strength solution in xylene). the molecular weight can be influenced by adding conventional regulators, such as aldehydes or thio compounds (eg. thioethanol or thioglycolic acid). Crosslinking by bifunctional comonomers, such as methylenebixsacrylamide, can also be used to increase the molecular weight.
C) Blocking of terminal groups and/or neutralization of the catalytic amounts of acid after polymerization is complete
In order to increase the efficiency and in particular to prolong the shelf life of the copolymers, it is advisable to carry out partial intramolecular esterification when polymerization is complete, or final blocking of any remaining free hydroxyl functions by reaction with anhydrides or isocyanates, and/or neutralization of any remaining catalytic amounts of acid with amines in order to avoid transesterification reactions, which may lead to gelling of the products.
Partial intramolecular condensation can be effected by heating the polymerization solution from B) to 100.degree.-140.degree. C. in the course of from 1 to 5 hours. Preferably, the polymerization solution in xylene from B) is heated for two hours at from 110.degree. to 120.degree. C. Further condensation may result in gelling.
The reaction of the free OH groups with anhydrides and isocyanates can be carried out directly after the polymerization or after partial intramolecular condensation, blocking of some of the remaining hydroxyl groups after the polymerization and subsequent condensation with azeotropic entraining agents with removal of water also being possible. A preferred procedure comprises blocking of all the terminal groups after partial intramolecular condensation at from 110.degree. to 120.degree. C. and/or blocking of from 60 to 80% of the hydroxyl groups present directly after polymerization with subsequent condensation by azeotropic removal of the water of reaction with the aid of an entraining agent, preferably xylene.
Blocking of the end groups is effected by adding or metering the desired amount of anhydride or isocyanate to the polymerization solution and heating the mixture to 70.degree.-120.degree. C. in the course of from 0.5 to 5 hours, in the presence or absence of a conventional catalyst. Preferred esterifying agents are acetic anhydride, phthalic anhydride and succinic anhydride.
If the terminal groups have already been blocked at the stage of the oxyalkylates or of the hydrophobic acrylates or methacrylates, condensation with the aid of an azeotropic entraining agent after the polymerization is preferred.
The neutralization of remaining catalytic amounts of acid from the esterification stage with amines is carried out in addition or alternatively to the blocking of the terminal groups. The neutralization is preferably effected after polymerization, condensation and any blocking of terminal groups with anhydrides or isocyanates are complete, with the result that esterification reactions which proceed to a further stage and may produce gelling are prevented.
Any catalytic traces of acid from the esterification reaction which are still present are neutralized by adding equimolar amounts of amines, eg. triethanolamine, tributylamine or triethylamine, to the solution of the polymer, in which the terminal groups may have been blocked, and carrying out the reaction for 2 hours at from 20.degree. to 80.degree. C. Complete neutralization can be detected via the amine number.
D) Modification of the polymer from B) and C) (optional)
In order to increase their efficiency and adapt them to the particular crude oil to be treated, it may be useful subsequently to modify the copolymers obtained under B) and C). Depending on the comonomers used in the copolymerization, the product may be modified in the following ways:
Modifications of the copolymer from C) is not restricted to the use of a single type of modification. Instead, any modifications according to 1) to 4) can be carried out one after the other.
Perhaps the most preferred copolymers for use as oil demulsifiers according to the invention are I) acrylates or methacrylates of oxyalkylates based on monohydric or polyhydric alcohols, preferably mono-to hexahydric alcohols, most preferably mono- to trihydric alcohols. These acrylic esters have an average molecular weight of from about 150 to 20,000, preferably from about 400 to 15,000, most preferably from about 800 to 10,000; copolymerized with II) the hydrophilic comonomers of the formula heretofore set forth. The mixture of these comonomers preferably contains about 10 to 100% by weight of acrylic and/or methacrylic acid, most preferably from about 40 to 100% by weight of acrylic and/or methacrylic acid.
The claimed copolymers according to the various embodiments of the invention have k-values in the range of about 8 to 100, more preferably about 12 to 40.
The described copolymers can be characterized and their synthesis reaction can be controlled by determination of the k-value, the acid number, the hydroxy number and/or the ester number. The crude oil demulsifiers are preferably employed as solutions, because they can be metered more readily in this form. Therefore, the claimed demulsification composition for crude oils can be yielded direct from polymerization process and/or by diluting the described copolymer with an organic solvent comprising the group of solvents which are used for the polymer synthesis. Also suitable solvents are lower alcohols, mixtures of lower alcohols with water esters and amides of carbon acids, tetrahydrofuran, dioxane, light and heavy naphtha fractions and mixtures of these solvents.
Where solutions are used, as is preferred, they advantageously contain from about 0.5 to 60 percent by weight of the active ingredient, i.e. the emulsion breaker. Optionally these solutions can be mixed with common additives like, for example, corrosion inhibitors, deoilers and defoamers. All mixing and diluting manipulations are carried out by vigorous stirring.
For breaking the crude oil emulsions, the solutions are preferably added to the crude oils at the well head. This makes it possible for demulsification to occur at the temperature of the freshly raised water-in-oil emulsion and at a speed such that the emulsion has already broken when it reaches the processing installation. There it is easily separated into clean oil and brine in a suitable separator, which may or may not be heated, with or without the aid of an electric field.
The demulsifier compositions are advantageously added to the crude-oil emulsions in amounts of from about 0.5 to 10,000 ppm, preferably from about 1 to 1000 ppm, and even more preferably from about 2 to 200 ppm, based upon the weight of the emulsion to be broken, at temperatures of from about 20.degree. to 80.degree. C.
The method of rapid removal of water is applicable to crude oil emulsions from a great variety of origins, for example those from north Germany, the North Sea, the Gulf States of the U.S., the Near and Middle East, and Africa, etc. The demulsification composition is preferably used for crude oil emulsions containing from about 1 to 99% of water.